Migrating from tsup to tsdown

Knowledge base for AI agents to migrate tsup projects to tsdown — the Rolldown-powered library bundler.

Runtime Requirement

tsdown requires Node.js 22.18.0 or higher to run (build-time only). The bundled output can still target lower Node.js versions via the target option, so a library that previously supported Node.js 18 / 20 with tsup can continue to do so after migrating.

Recommended workflow when supporting Node.js 18 / 20:

• Build with Node.js 22+ in CI, setting an explicit target such as 'node18' or 'node20'.
• Test the built output (or the packed tarball) on the lower Node.js versions you need to support.

When to Use

• Migrating a project from tsup to tsdown
• Understanding differences between tsup and tsdown options
• Reviewing or fixing post-migration configuration issues
• Advising users on tsup→tsdown compatibility